The requirements for studying the epidemiology of fungal pathogens are analysed and a controlled environment chamber is described which was developed to meet these requirements. It allows accurate reproduction of a wide range of combinations of the most relevant climatic factors influencing the development of fungal diseases on plants, namely, air temperature, air humidity and dew formation. Dew can be simulated by means of a transparent radiative panel placed in the ceiling of the chamber. Data on condensation of natural dew on the leaves of tomato plants are presented and the elements of the energy balance during the dew formation are analysed. Finally, the performance of the system is discussed and improvements are proposed.